The present invention relates to an apparatus and method for removing spatter which has accumulated on the nozzle of an arc welding torch. More particularly, the present invention relates to an apparatus and method for removing spatter from an arc welding torch nozzle whereby a single control power unit and control logic may be used to operate multiple electromagnetic spatter removal devices.
Manufacturing operations employ various arc welding processes when creating a product. Typically, a welding electrode is placed near articles to be welded and an electrical arc is formed between the electrode and the articles, such that the articles temperature is locally raised to thereby cause the articles to melt and form a weld.
A particularly useful method of arc welding is that of a continuous electrode shielded by an inert gas. Utilizing such a technique, requires a nozzle be placed around the welding electrode, such that inert gas is directed towards the area to be welded. The shielding gas is needed to prevent the atmosphere from adversely affecting the weld. For example, the gas prevents unwanted oxidation of the parts, as well as maintains the physical properties of the welded area. When such a process is utilized, a common problem arises; weld spatter accumulates on the opening of the nozzle. Over time, this accumulation will become so great as to block the flow of shielding gas. When the flow of shielding gas is blocked, the mechanical properties of the weld will be adversely affected.
Various devices have been proposed to remove spatter from the nozzle of an arc welding torch. A method and device which has proven to be highly acceptable is the mechanism and method for electromagnetic removal of spatter on the nozzle of an arc welding torch. Such a device is denoted in U.S. Pat. No. 4,838,287, which is hereby incorporated by reference.
One detriment of electromagnetic spatter removal devices known at the present time is that the controller of the devices is configured to control only one device at a time. For each device, a control and a power supply is needed to charge the coil of the electromagnetic spatter removal device at the appropriate time.
It has been determined, however, that in facilities where multiple-welding stations exist, such as in many manufacturing and assembly plants, a significant amount of time can exist between the electromagnetic spatter removal of one torch nozzle at one station and the required electromagnetic spatter removal of another torch at another station. These stations may also be located in such a manner that the devices carrying the welding torch may not be able to reach a central location for spatter removal. Thus, it would be desirable to utilize a device that is capable of controlling multiple spatter removal devices utilizing a single power source, thereby reducing the number of power and control units necessary and thereby reduce the overall cost associated with the spatter removal process of the individual torch nozzles.
It is therefore, an object of the present invention to provide an apparatus and method whereby a single power and control unit may be utilized for firing multiple electromagnetic spatter removal devices.
In a first disclosed embodiment, a weld spatter removal device utilizes an existing power supply. The source of power is connected to a silicon control rectifier (SCR) which in turn is connected to a multiple contactor switch mechanism mounted in an enclosure. The multiple electromechanical contactor switch mechanism is utilized to selectively allow the passage of current to individual electromagnetic coils. The contactor switch mechanism is connected to at least two contactors, which in turn are connected to at least two electromagnetic coils, which are charged to remove weld spatter from the opening of the nozzle of an arc welding torch. A control mechanism is included in the enclosure and is utilized for the selection of the appropriate contactor to be energized. The selection is determined by input from the user or customer""s welding cell controller or robot.
There is also disclosed a method for utilizing a single control and power source to control multiple weld spatter removal devices. The method includes the steps of: (1) providing a power supply connected to a SCR, (2) providing a contactor switch mechanism with at least two switches, (3) providing a control mechanism connected to the contactor switch mechanism, (4) Providing at least two electromagnetic coils connected to at least two electromechanical contactors, (5) energizing the first switch, (6) closing the first contactor, (7) energizing the power supply, (8) opening the first switch, (9) energizing another switch, (10) closing another contactor, (11) energizing the power supply (12) opening the switch just energized.
In a second embodiment, a weld spatter removal device utilizes an external source of power connected to a circuit breaker. A bridge rectifier is connected to the circuit breaker and a first resistor is connected to the bridge rectifier. A capacitor bank for storing a charge is connected to the first resistor. There is also a second resistor connected across the capacitor bank through a relay for discharging the capacitor bank when the power is turned off. The second embodiment also includes at least two silicon controlled rectifiers connected to the capacitor bank and at least two electromagnetic coils connected to the at least two silicon controlled rectifiers for generating a magnetic field to remove weld spatter from an arc welding nozzle. There is also a control logic board for receiving and generating control signals to regulate the energizing of the at least two electromagnetic coils.